Blow-off valve



No. 607,265. Patented July I2, i898. D. McLEAN.

BLOW-OFF VALVE.

(Application filed Jan. 5, 1898.)

( No Model.)

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UNTTED STATES PATENT Trice.

DAVID McLEAN, OF CHICAGO, ILLINOIS.

BLOW-OFF \IIALVE.

SPECIFICATION forming part of Letters Patent No. 607,265, dated July 12,1898.

Application filed January 5,1898. Serial No. 665,649. (No model.)

To all whom, it nuty concern:

Be it known that I, DAVID MCLEAN, a citizen of the United States,residing in Chicago, in the county of Cook and State of Illinois, haveinvented a new and useful Improvement in Blow-Off Valves forLocomotives, of which the following is a specification.

In this invention I have endeavored to make the valve movements entirelyindependent of any direct action of the steam from the boiler and alsoto make the valve and its seat of a form capable of opening widely, soas to form a large and unrestricted opening; also, to make the valve andits seat of such form as will obviate the lodgment of scale or sedimentbetween them and the consequent inability to absolutely shut off thedischarge. The construction by which these objects are attained will befully understood from the description given below and from theaccompanying drawings, in which Figure 1 is an elevation of myinvention; and Fig. 2*is a central section thereof, the latter Viewshowing also the air-valve for controlling the blow-off valve.

In said drawings, A represents the valve box or casing, having openingsA A at 0pposite ends of the valve-passage A one opening connecting withthe boiler and the other with the discharge.

The blow-off valve is shown at B and is preferably of the gate variety,havinga movement at right angles to the passage A Its outline isindicated by the broken line B in 1, and upon its flat sides it ispreferably made tapering, as shown at Fig. 2. Of course the walls of thepassage are recessed to correspond with the valve, and below its seat isa cross-opening A connecting with the opening A, through which thevalve-seat and passage may be cleaned. It will be noticed that when thisvalve moves into its closed position it is apt to push any scale lodgingalong the Walls of its seat ahead of it either into the main passage orinto the cross-openingA The movements of the valve 13 are not caused inany way by the steam-pressure acting directly upon the valve, butinstead thereof it is preferably moved in both directions between guidesC C, which extend upward from passage A into the upper part of thevalve-box, as seen at Fig. 1, by air-pressure acting upon the piston Din cylinderD, such piston being joined to valve B by the stem The airfor operating this motorpiston is supplied through the pipe D and thebranches D and D one branch leading to the top and the other leading tothe bottom of the cylinder, as plainly indicated. The valve D which isunder the control of the engineer and preferably by means of leverswhich he can operate from his cab, controls the air from pipe D anddirects it, as desired,to either side of the piston. As shown, theair-pressure is acting upon the top of the piston and the blow-off valveis closed, and

atthe same time the exhaust-port D of the valve is in communication withthe under side of the piston. If a quarter-turn be now given to thevalve, the compressed air will be directed under the piston, therebyopening Valve B, and at the same time the air above the piston will begiven exit through the valve D and port D".

A stuffing-box E is placed around the stem 13 as shown, and acoil-spring F, encircling said stem, is arranged between the top of boxA and the top of valve B, its tension being exerted down upon the valvein order that the latter may not open until the air-pressure underpiston D becomes sufficient to overcome the spring.

It will be also noticed that when the valve B is open a straight andunrestricted channel of large capacity is afforded for the passage ofthe water, mud, scale, 850., from the boiler, through which solids maybe blown.

By turning the air-valve so as to open the branch D or D only part wayand then closing it before the piston has moved its entire stroke theblow-off valve may be moved to and held in a partially-open position.This is frequently desirable.

It will be noticed that the movement of the valve B is at right anglesto the direction in which the steam-pressure from the boiler is exertedagainst the valve; also, that the valve is stayed by the guides againstthe steampressure in any partially-open position as well as in itsclosed position; also that in closing it moves in a directionsubstantially parallel to the guides and to the faces of its seat and isthus adapted to force out any pieces of scale lodged against the guidesor seat.

IVhile I have shown the form of apparatus which I deem the best, it willbe obvious that other forms of valves may be substituted for the valveillustrated without departing from my invention, the chief requisitebeing that the valve be not moved by the steam acting directly againstit. I also do not Wish to be limited to the relative arrangement shownof the valve and its actuating means, nor to the construction describedof the actuating means, nor to actuating means adapted to move the valveback and forth in a straight line, as obviously the actuating devicesmust be adapted to impart the motion required by the valve; nor do IWish to be limited in all my claims to a piston adapted to actuate thevalve in both directions, as it is obvious that the spring shown mightbe utilized for moving it in one direction, and in that case one of theair connections of cylinder D would be unnecessary.

I claim-- 1. The combination With the valve closing the blow-offpassage, such valve being unaffected by the steam pressing against it,of means for moving said valve, andthe spring F, substantially asspecified.

2. The combination with the valve closing the blow-off passage, suchvalve being unaffected by the steam pressing against it, of means forboth opening and closing said valve, and a springacting to retain thevalve in its closed position, substantially as specified.

3. The combination with the valve closing the blow-off passage, suchvalve being unaffected by the steam pressing against it, of a motor foropening the Valve, and a spring tending to close it, substantially asspecified.

DAVID MULEAN.

\Vi tnesses:

EDWARD EvAn'rs, II. M. JVIUNDAY.

